The Playfair cipher http://en.wikipedia.org/wiki/Playfair_cipher is based on a 5 by 5 character array that treats i and j as equivalent:
paswo rdbce fghik lmnqt uvxyz To encode “All is discovered flee” you replace pairs of letters al li sd is co ve re df le ex with pairs diagonally opposite, one to the right, or one below (wrapping) from the table, getting pm qf ab hw ew zd dr rg tr bz Your mission, should you decide to accept it, is to write j code for enciphering and deciphering, given the five by five table. That’s the easy part. The hard part is to design and implement an analogous cipher that uses the 3 by 3 by 3 character array below to replace triples of letters alx _is _di sco ver ed_ fle ex_ pas wor dbc efg hij klm nqt uvx yz_ ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
